PARENT SESSION
Contributed Oral Session 40: Forest Understories
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal
Relationships between ground layer herbs and stand dead and living trees in a central Illinois old-growth forest.
Smith, Japhia1, Anderson, Roger*,2, 1 USDA APHIS (Animal and Plant Health Inspection Service), Chicago, Illinois2 Illinois State University, Normal, Illinois
ABSTRACT- We studied species composition and abundance of trees and herbaceous plants and standing dead trees in a 27 ha old-growth forest, in central Illinois, USA (40°21.2'N, 89°7.7'E). Using a stratified random sampling scheme we established 105 permanent sampling plots on a 50 m x 50 m grid. Current woody vegetation and standing dead trees on the site were sampled using 0.07 ha circular quadrats. Four one-meter square quadrats were used to collect presence/absence data for herbaceous vegetation in each tree quadrat. Tree and herb data were analyzed separately using Cluster Analysis and Nonmetric Multidimensional Scaling (NMS). There was an overall significant relationship between tree cluster analysis groups and herb NMS axis scores (Pillai's trace=0.252, df=8,198, p=0.0007). However, follow-up protected ANOVAs on each of the four NMS axes indicated that only axis 2 was significant (F=6.74, df=2, 101, p=0.0018). Axis 2 of the herb ordination represented only a small portion (11.6%) of the total variation. Correlation analysis on the four NMS tree axes and herb axes indicated that three correlations were statistically significant (Bonferroni alpha = 0.0031). However, several of the significant correlations were among axes that each represent <12% of the ordination variation. Despite some significant relationships among trees and herbs overall, the results suggest that the underlying environmental, temporal, and/or spatial gradients controlling the tree composition and abundance are not the same as those controlling the herbaceous species. There was a significant ANOVA (F=12.87, df=2, 101, p<0.0001) on the density of standing trees with herb groups. Mean ± SE standing dead (trees/ha) in herb groups were: group A (30.8±3.8), group B (11.0±2.1), and group C (12.1±2.6). These results implicated a possible light effect, i.e. more standing dead means less canopy, more light, and a possible effect on either species abundance or species composition.
Key words: tree herb relations, standing dead trees, old-growth forest, cluster analysis NMS